Acid Fluoride Research Articles

Taking Olefin Metathesis to the Limit: Stereocontrolled Synthesis of Trisubstituted Alkenes.

ConspectusIn this Account, we share the story of the development of catalytic olefin metathesis processes that efficiently deliver a wide range of acyclic and macrocyclic E- or Z-trisubstituted alkenes. The tale starts with us unveiling, in collaboration with Richard Schrock and his team, the blueprint in 2009 for the design of kinetically controlled Z-selective olefin metathesis reactions. This paved the way for the development of Mo-, W-, and Ru-based catalysts and strategies for synthesizing countless linear and macrocyclic Z-olefins. Six years later, in 2015, we found that abundant Z-alkene feedstocks, such as oleic acid, can be directly transformed to high-value and more difficult-to-access alkenes through a cross-metathesis reaction promoted by a Ru-catechothiolate complex that we had developed; the approach, later coined stereoretentive olefin metathesis, was extended to the synthesis of E-alkenes.It was all about disubstituted alkenes until when in 2017 we addressed the challenge of accessing stereodefined Z- and E-trisubstituted alkenes, key to medicine and materials research. These transformations can be most effectively catalyzed by Mo monoaryloxides pyrrolide (MAP) and chloride (MAC) complexes. A central aspect of the advance is the merging of olefin metathesis, which delivered trisubstituted alkenyl fluorides, chlorides, and bromides with cross-coupling. These catalytic and stereoretentive transformations can be used in various combinations, thereby enabling access to assorted Z- or E-trisubstituted alkene. Ensuing work led to the emergence of other transformations involving substrates that can be purchased with high stereoisomeric purity, notably E- and Z-trihalo alkenes. Trisubstituted olefins, Z or E, bearing a chemoselectively and stereoretentively alterable F,Cl-terminus or B(pin),Cl-terminus may, thus, be easily and reliably synthesized. Methods for stereoretentive preparation of other alkenyl bromide regioisomers and α,β-unsaturated carboxylic and thiol esters, nitriles, and acid fluorides followed, along with stereoretentive ring-closing metathesis reactions that afford macrocyclic trisubstituted olefins. Z- and E-Macrocyclic trisubstituted olefins, including those that contain little or no entropic support for cyclization (minimally functionalized) and/or are disfavored under substrate-controlled conditions, can now be synthesized. The utility of this latest chapter in the history of olefin metathesis has been highlighted by applications to the synthesis of several biologically active compounds, as well as their analogues, such as those marked by one or more site-specifically incorporated fluorine atoms or more active but higher energy and otherwise unobtainable conformers.The investigations discussed here, which represent every stereoretentive method that has been reported thus far for preparing a trisubstituted olefin, underscore the inimitable power of Mo-based catalysts. This Account also showcases a variety of mechanistic attributes─some for the first time, and each instrumental in solving a problem. Extensive knowledge of mechanistic nuances will be needed if we are to address successfully the next challenging problem, namely, the development of catalysts and strategies that may be used to synthesize a wide range of tetrasubstituted alkenes, especially those that are readily modifiable, with high stereoisomeric purity.

Role of starch in one pot fabrication of mesoporous gamma-alumina with excellent fluoride sorption capacity

Green synthesis of mesoporous γ-AƖ2O3, a cutting-edge material for sustainable application in medicine, engineering, energy, and water treatment, is still challenging. Our study used a one-pot strategy for facile synthesis of γ-AƖ2O3 by sol-gel method using starch from cassava waste. AƖ(OH)3 were bound to the O-H groups of the starch molecule to form the AƖ(OH)3-starch complex in a nano-network confined in starch polymer cages. Its calcination at 500 ℃ produced a mesoporous, highly crystalline water stable γ-AƖ2O3 with a pore size of 2.07 nm and an extensive BET surface area (215 cm2/g). Using the response surface methodology (RSM), the as-synthesized γ-AƖ2O3 was optimized for efficient fluoride removal from water. A central composite design (CCD) was used to study the effect of initial fluoride concentration, pH, contact time, and sorbent dose on fluoride removal efficiency and optimization of the process. The relative importance of the sorption process variables to the fluoride removal process was assessed using ANOVA. The quadratic model showed that the predicted response was significantly correlated with the experimental response (R2 = 0.9667), with sorbent dose and pH being the process's most influential factors. Optimum conditions for 93.6% fluoride removal efficiency were sorbent dose of 0.5 g, initial fluoride concentration of 10 mg/L, pH 7, and contact time of 137.5 min. A weakly acidic medium favored fluoride removal from water, while the presence of PO43- and HCO3- retarded the process. The sorption data fitted well in the Langmuir isotherm (0.9783) and pseudo-second-order kinetic model (0.9999), indicative of a chemisorption process. The maximum sorption capacity towards fluoride was 207.5 mg/g. A thermodynamic study indicated that the sorption process was spontaneous and endothermic, with increased randomness at the solid-solution interface. Sorption, desorption, sustainability, and leaching tests showed that the sorbent could be used for sustainable fluoride removal at 8.3 USD/1000 liters of safe drinking water.

Microwave-etched V2C MXene-activated carbon hybrid as a high-performance anode material for lithium-ion batteries

Activated carbon (AC) has been widely utilized as an active material in lithium-ion batteries (LIB) due to its stability and abundance. Nevertheless, the performance of AC anode materials alone falls short of competing with hybrid anode materials, which can attain maximum discharge capacity. Recently, a new two-dimensional (2D) transition metal carbide, MXene, has shown promising performance as an anode in LIB applications. The combination between AC and MXene has proved to improve battery performance previously. Thus, in this study, the electrode was prepared using a hybrid of activated carbon with vanadium carbide MXene (V2C), which was synthesized by etching V2AlC with in situ of hydrochloric acid (HCl) and lithium fluoride (LiF) at 90 °C for 30 min via microwave-assisted hydrothermal technique. The characterization by XRD pattern shows the appearance of V2C MXene peak at 7.23°, indicating the successful etching from V2AlC MAX. The as-prepared AC/V2C_D at ratio 9:1 revealed excellent electrochemical properties as anode LIB, owned capacity up to 562 mAh g−1 (at 50 mA g−1) with cycling stability and columbic efficiency of 95.87 % and 98.2 %, respectively after 50 cycles. Moreover, AC/V2C_D exhibited the smallest Rct (18.50 Ω), and the discharge capacity of 370.25 mAh g−1 was restored after 60 cycles when the current density returned to 50 mAg−1, implying a good reversibility performance and high endurance for LIB. Furthermore, the fabricated full cell of AC/V2C_D//LiFePO4 exhibits initial discharge and charge capacity at 159.6 and 199.8 mAh g−1, respectively, with 79.9 % of CE and delivers a stable cycling performance with reversible discharge specific capacity of 82.72 mAh g−1 after 100 cycles. These promising results prove that the hybrid of AC/V2C_D MXene can be good potential as an anode material in future LIBs applications.

Post-Synthesis of HZSM-5 by Aluminum Fluoride in an Acidic Fluoride Solution for Enhanced Reforming of Lignite Pyrolytic Volatiles into Light Aromatics

Post-Synthesis of HZSM-5 by Aluminum Fluoride in an Acidic Fluoride Solution for Enhanced Reforming of Lignite Pyrolytic Volatiles into Light Aromatics

Reinforced PTFE composites with atomized powder of Inconel 625 alloy for sealing application: Study of structural properties and molecular dynamics simulation

Polytetrafluoroethylene (PTFE) is one of the most used materials for sealing applications. Despite remarkable properties, PTFE has poor wear resistance which causes leakage problems during sealing. Studies have shown that the most important factor for improving the sealing properties of the PTFE matrix is adding suitable fillers as the reinforcing phase. Therefore, the design and fabrication of the PTFE-based composite with new reinforcements is a highly demanded research to enhance sealing properties. In this investigation, atomized powder of the Inconel 625 alloy which is a Nickel-based superalloy was used as a reinforcing phase to fabricate the PTFE-based composite. The effect of different weight percentages of the Inconel 625 was investigated on the wear, corrosion, and leak rate properties of the PTFE-based composites. The result showed that the predominant abrasion mechanism of the PTFE/Inconel 625 composite is the usually adhesive type with proper corrosion resistance against hydrochloric acid, sulfuric acid, and hydrogen fluoride. Among the fabricated composites, the mixture of 50 % Inconel 625 alloy and 50 % PTFE exhibited the best combination of properties with a leak rate of approximately 10−9 mbar L s−1. Besides, the molecular dynamics (MD) simulation was applied to study the interface of the PTFE and the Inconel 625 alloy particles, the wear, and the permeability behavior of the composites. Based on the obtained results, the novel PTFE composite can be applied as a sealing application for industrial purposes.

Borane derivatives of five-membered N-heterocyclic rings as frustrated Lewis pairs: activation of CO2

The reaction of seventeen borane derivatives of five-membered N-heterocyclic rings (BNHRs) with CO2 has been studied by means of DFT calculations. Several non-covalent complexes between the BNHRs and CO2 which evolve through a TS in a single adduct for each BNHR have been identified. The calculated IRC of the TS has allowed to identify the non-covalent complex involved in the reaction in each case. The stationary points of the reactions have been analyzed with the distortion/interaction partition model. In addition, empirical models have been attempted to correlate the acid (fluoride ion affinity) and basic (proton affinity) properties of the isolated BNHR with the TS barriers and adduct energies. The energetics of the reactions are influenced by the number of nitrogen atoms in the ring.

Intermolecular interaction engineering to enhance Lithium-Ion storage in Two-Dimensional oxidized silicon nanosheet anodes

Unlike conventional Si anodes for use in Li-ion batteries, 2D oxidized Si nanosheets, i.e., siloxene, undergo negligible volume expansion during cycling owing to their unique geometries and chemical structures. Nevertheless, siloxene receives less attention than other Si-based nanostructures, partly because the interactions of siloxene with conventional binders and their effects on charge storage are largely unexplored. Herein, the intermolecular interactions of siloxene with four typical binders (alginate, carboxymethyl cellulose, polyacrylic acid, and α-polyvinylidene fluoride) are investigated to enhance the electrochemical performance using a simple method. The binders are selected using two criteria, i.e., polarity and functional groups, and they exhibit different intermolecular interactions with siloxene. Particularly, alginate forms the strongest intermolecular bonds, which are attributed to dipole–dipole attractions between the H atoms in siloxene and the OH groups in alginate. The trend of the intermolecular binding strengths of the binders is consistent with those of the cycling stabilities and rate performances. The alginate-based siloxene electrode displays an excellent charge capacity retention of 66 % after 500 cycles at 200 mA g−1, which is unprecedented for pristine siloxene anodes. This study provides useful guidelines for designing binders for use in electrode materials with chemical structures similar to that of siloxene.

Exogenous Auxin and Gibberellin on Fluoride Phytoremediation by Eichhornia crassipes.

High rates of fluorosis were reported worldwide as a result of human consumption of water with fluoride contents. Adjusting fluoride concentration in water as recommended by the World Health Organization (<1.5 mg L-1) is a concern and it needs to be conducted through inexpensive, but efficient techniques, such as phytoremediation. The application of phytohormones was investigated as a strategy to improve this process. Thus, the main goal of this research was to evaluate the effect of exogenous auxin and gibberellin on the tropical duckweed Eichhornia crassipes performance for fluoride phytoremediation. Definitive screening and central composite rotatable designs were used for experiments where fluoride concentration (5~15 mg L-1), phosphorus concentration (1~10 mg L-1), and pH (5~9) were assessed as well throughout 10 days. Fluoride contents were determined in solution and plant tissues by potentiometry. Higher concentrations of fluoride reflected on greater absorptions by plants, though in relative terms removal efficiencies were quite similar for all treatments (~60%). Auxin and acidic conditions favored fluoride removals per mass of plant. Fluoride accumulated mostly in leaves and auxin probably alleviated toxic effects on E. crassipes while gibberellin showed no effect. Therefore, E. crassipes could be employed as a fluoride accumulator plant for water treatment and exogenous auxin may be used to improve the process.

The first example of fluoro-Meinwald rearrangement

Novel fluorinated norbornadienes were synthesized in up to 95% yield by the base-induced elimination of HNO2 from 5-fluoro-5-nitro-6-arylbicyclo[2.2.1]hept-2-enes prepared, in turn, by the Diels–Alder reaction of β-fluoro-β-nitrostyrenes with cyclopentadiene. The subsequent epoxidation initiated the Meinwald type rearrangement affording 6-aryl-bicyclo[3.1.0]hex-2-ene-6-carboxylic acid fluorides as individual (1SR,5RS,6RS)-diastereomers. The transformation is the first example of fluoro-Meinwald rearrangement to form the corresponding acyl fluorides.

Z-Trisubstituted α,β-Unsaturated Esters and Acid Fluorides through Stereocontrolled Catalytic Cross-Metathesis.

Catalytic cross-metathesis (CM) reactions that can generate trisubstituted alkenes in high stereoisomeric purity are important but remain limited in scope. Here, CM reactions are introduced that generate Z-trisubstituted α-methyl, α,β-unsaturated, alkyl and aryl esters, thiol esters, and acid fluorides. Transformations are promoted by a Mo bis-aryloxide, a monoaryloxide pyrrolide, or a monoaryloxide chloride complex; air-stable and commercially available paraffin tablets containing a Mo complex may also be used. Alkyl, aryl, and silyl carboxylic esters as well as thiol esters and acid fluoride reagents are either purchasable or can be prepared in one step. Products were obtained in 55-95% yield and in 88:12->98:2 Z/E ratio (typically >95:5). The applicability of the approach is highlighted by a two-step conversion of citronellol to an isomintlactone precursor (1.7 g, 73% yield, and 97:3 Z/E) and a single-step transformation of lanosterol acetate to 3-epi-anwuweizic acid (72% yield and 94:6 Z/E). Included are the outcomes of DFT studies, regarding several initially puzzling catalyst activity trends, providing the following information: (1) it is key that a disubstituted Mo alkylidene, generated by a competing homo-metathesis (HM) pathway, can re-enter the productive CM cycle. (2) Whereas in a CM cycle the formation of a molybdacyclobutane is likely turnover-limiting, the collapse of related metallacycles in a HM cycle is probably rate-determining. It is therefore the relative energy barrier required for these steps that determines whether CM or HM is dominant with a particular complex.

Sustainable synthesis of vanadate/fluorapatite nano-crystallites from solid waste for enhanced photocatalysis and pollution removal

In this work, vanadate-fluorapatite, V2O5/Ca10(PO4)6F2, nanocrystals were successfully synthesized through a straightforward one-step co-precipitation method. This method was based on two toxic solid wastes, which are mainly generated as by-products during sulfuric acid manufacturing and in the phosphate industry. The two solid wastes were mainly based on phosphogypsum as a source of calcium and vanadium pentoxide as a source of vanadate. In comparison to numerous conventional methods for FAP synthesis, this innovative method is not laborious, not complex, cost-effective, and environmentally friendly, thanks to the recovery of toxic solid wastes. Furthermore, it consists of mixing various contents of anhydrous gypsum with phosphoric acid, vanadium pentoxide, and ammonium fluoride at one time and at room temperature with no further adjustment of the pH. Several physicochemical characterization techniques were used, including X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), and Ultraviolet-Visible Spectroscopy (UV-vis). Whereas SEM analysis of the crystals obtained showed a nanometer-scale fluorapatite crystallites was obtained. The obtained results offer exciting potential for applying the prepared nanomaterial in both photocatalysis and pollution removal. They hold great promise and are expected to generate significant interest in these fields.

Changing the reaction pathway in TiO2 photocatalytic dehalogenation of halogenated aromatic pollutants by surface hydroxyl regulation.

Understanding the photocatalytic reductive dehalogenation mechanism of halogenated aromatic pollutants is of great research value. However, the proton source in the photocatalytic dehalogenation process of representative halogenated aromatic pollutants by TiO2 is not clear. In this study, the TiO2 surface was modified by hydrochloric acid, sodium hydroxide, and sodium fluoride to obtain TiO2 samples with different hydroxyl groups. It was found that the hydroxyl groups on the surface of TiO2 affects the sequence of proton and electron transfer in dehalogenation. The abundance of hydroxyl groups on the surface of TiO2 can accelerate the reductive dehalogenation process of representative halogenated aromatic pollutants. The kinetic solvent isotope effect was used to study the proton-coupled electron transfer process in the reaction. It shows that the enriching of protons on TiO2 bridging oxygen (bridging hydroxyl groups) is conducive to the rapid step of protonation of the reactant, and subsequent proton and electron transfer. On the contrary, the bridging hydroxyl groups can be removed by reacting with strongly basic sodium hydroxide and sodium ions can occupy the bridging oxygen. The substitution of bridging oxygen by fluorine ions can also lead to the destruction of bridge hydroxyl groups. Significantly, the absence of bridging hydroxyl groups on titanium dioxide will lead to the dehalogenation of representative halogenated aromatic pollutants initiated by electron transfer. This study is helpful to understand dehalogenation reaction paths catalyzed by TiO2.

A cycloruthenated 2-phenylimidazole: chromogenic sensor for nitrite in acidic buffer and fluoride in CH3CN

A cycloruthenated 2-phenylimidazole as a colorimetric sensor can detect fluoride in CH3CN by a great red-shift in absorption. However, it demonstrated sensitivity and selectivity to nitrite rather than fluoride in acidic buffer.

A (TD-)DFT study on photo-NHC catalysis: photoenolization/Diels-Alder reaction of acid fluorides catalyzed by N-heterocyclic carbenes.

A comprehensive mechanistic study on the N-heterocyclic carbene (NHC) catalyzed photoenolization/Diels-Alder (PEDA) reaction of acid fluorides was performed in the framework of (time-dependent) density functional theory ((TD)-DFT). The 1,5-hydrogen atom transfer (1,5-HAT) during photoenolization of an ortho-toluoyl azolium salt was found to be feasible via, first, singlet excitation and photoenolization, and then, after crossing to the triplet manifold, populating a biradical dienol which allows for the formation of two ortho-quinodimethane (o-QDM) isomers due to a low rotational barrier. The (Z)-isomer is mostly unproductive through sigmatropic rearrangement back to the starting material while the (E)-isomer reacts in a subsequent concerted Diels-Alder reaction likely as the deprotonated dienolate. The experimentally observed diastereoselectivity is correctly predicted by theory and is determined by a more favorable endo trajectory in the cycloaddition step. These findings demonstrate that ortho-toluoyl azolium species exhibit similar photophysical properties as structurally related benzophenones, highlighting the unique ability of the NHC organocatalyst to transiently alter the excited state properties of an otherwise photoinactive carboxylic acid derivative, thereby expanding the scope of classical carbonyl photochemistry.

Design and synthesis of TiO2/Ti3C2 composites for highly efficient photocatalytic removal of acetaminophen: The relationships between synthesis parameters, physicochemical properties, and photocatalytic activity

In this study, we report the potential of TiO2/Ti3C2 composite fabricated by oxidation of MXene for degradation of persistent organic pollutants. The effect of the synthesis conditions (time, temperature, and reaction environment) on the morphology, physicochemical properties, and photocatalytic activity was investigated. It was found that acetaminophen degradation was positively correlated with TiO2 content in the composite structure. Furthermore, the findings confirmed that the synthesis reaction environment strongly influenced the obtained materials photocatalytic activity. The TiO2/Ti3C2 composite obtained by solvothermal route in the presence of hydrochloric acid and ammonium fluoride exhibited the highest efficiency towards acetaminophen degradation than other composite materials, for which ACT removal reached 92 % within 60 min of irradiation under simulated solar light. The improved photocatalytic performance can be attributed to the presence of anatase-rutile polymorphs exposing highly active { 0 0 1} and { 1 0 1} facets coupled with MXene. Superoxide anion radicals and hydroxyl radicals played a major role in ACT degradation. Moreover, 3-hydroxyacetaminophen was detected as the first intermediate of ACT degradation, leading quickly to aromatic ring opening and production of aliphatic acids. Overall, this work provides an effective strategy for designing novel and efficient MXene-based photocatalysts for the degradation of emerging contaminants in water systems.

Synthesis of 2D titanium carbide Ti2C, its characteristics, and nonlinear optical properties

Various scientists have widely explored two-dimensional (2D) materials to study their unique properties for a wide range of exciting opportunities in multiple fields. Among the highly investigated 2D materials, a new fast-growing family of 2D materials called MXenes has been fabricated and developed rapidly. This study offered a methodology to synthesize Ti2C using the same etching method but with two different enchants, namely, hydrofluoric acid (HF) and in situ generated HF using hydrochloric acid (HCl) and lithium fluoride (LiF) salt. The characteristics of the synthesized MXenes were studied and characterized using HRTEM, AFM, FESEM, EDX, FTIR, UV–Vis NIR, and TGA, and their nonlinear optical properties were also analyzed. The results indicate that the synthesized Ti2C–HF and Ti2C–HCl have 2D multilayered nanostructures with thicknesses ranging from 10 nm to 20 nm. EDX and FTIR results show the presence of Ti, C, and a few Al functional groups, which suggests the success of the etching process. The UV–Vis analysis shows the absorption band at about 200–250 nm. In addition, the thermal stability of both MXenes was observed, and the nonlinear optical properties of the as-synthesized MXenes were also studied. These MXenes display good potential to be applied as a saturable absorber in pulsed laser generation for future photonics applications.

Acidic properties of Al-rich ZSM-5 crystallized in strongly acidic fluoride medium

The fluoride medium synthesis of zeolites, especially in the strongly acidic regions, yields products with unique characteristics such as ultra-hydrophobic surfaces and defect-free lattices. However, it is often difficult to incorporate aluminum into the framework of zeolites in this medium, limiting the acquisition and development of catalytic materials. The present paper shows that inter-zeolite transformation is efficient for obtaining ZSM-5 zeolites with lower Si/Al ratios in a strongly acidic fluoride medium. The critical point is that the parent zeolites can retain some locally ordered fragments during their dissolution, including framework Al atoms, and incorporate them into the ZSM-5 product. The acidic properties of the trans-crystallization products obtained in an acidic medium display significant differences from the traditional ZSM-5 with a similar Si/Al ratio in the amounts, strength, and types of the acid sites; thus, they behave differently in typical acid-catalysed reactions, such as dehydration of alcohols.

Synthesis and Chemoresistive Properties of Single-Layer MXene Ti2CTx

As part of the study, we have developed a method for obtaining a single-layer Ti2CTx MXene by the interaction of Ti2AlC with a mixture of hydrochloric acid and sodium fluoride followed by delamination using a tetramethylammonium hydroxide solution and ultrasonic exposure. The obtained stable aqueous dispersion of Ti2CTx has been applied by microplotter printing onto a specialized sensor chip, which has been dried at a temperature of 150°C under reduced pressure. The coating has been studied using modern physicochemical methods of analysis. According to the data of X-ray spectral elemental microanalysis, the ratio n(Ti) : n(F + Cl) = 2 : (0.82–0.85), n(F) : n(Cl) ≈ 6 : 4; aluminum impurity does not exceed 1.5–2.0%. Data have been obtained on the local electrophysical properties of the Ti2CTx coating: on the value of the electron work function from the surface of the material, the distribution of charge carriers, and the capacitance gradient of the “probe tip–sample microregion” capacitor. For the first time, at an operating temperature of 30°C, extremely high chemoresistive responses of the Ti2CTx receptor layer to the content of 1 and 5% oxygen in nitrogen have been determined, which amounted to 8.6 and >276, respectively.

Mussel-Inspired Hydrogels for Fluoride Delivery and Caries Prevention

Fluoride agents hold promise for the repair and prevention of caries lesions, but their interaction with enamel is often hampered and diminished because of the dynamic wet environment in the oral cavity, which affects the efficacy of fluoride delivery and limits treatment success. We herein developed a mussel-inspired wet adhesive fluoride system (denoted TS@NaF) fabricated by the self-assembly of tannic acid (TA), silk fibroin (SF), and sodium fluoride (NaF). TS@NaF demonstrated remarkable biological stability and biocompatibility, showed reliable wet adhesion, released fluoride ions (F−) topically, and induced significant deposition of calcium fluoride (CaF2) onto enamel in vitro. Furthermore, TS@NaF provided an anticaries effect in vitro and induced a detectable increase in enamel mineral density. Advanced fluoride-releasing bioadhesives are therefore promising candidates for caries prevention and highlight the great potential of mussel-inspired dental materials in clinical applications.

Color changes and shear bond strength to simulated caries lesions treated with a novel solution of 20% silver nanoclusters in polymethacrylic acid

The aims of the study were: (1) To compare the staining effect on demineralized dentin simulating caries between silver nanoclusters (AgNCls) synthesized using polymethacrylic acid (PMAA) and silver diammine fluoride (SDF), and (2) to measure the shear bond strength (SBS) of a glass ionomer cement (GIC) to simulated caries lesions with and without the application of AgNCls/PMAA or SDF. Dentine blocks 4 mm thick from twenty-four non-carious third molars were sectioned and coated with nail varnish (Revlon, New York, USA). Simulated caries lesions on occlusal dentin surfaces were created (66 h in 0.05 M acetate buffer 2.2 mM calcium/phosphate pH 5.0). Specimens were divided into groups and treated with (n = 8): (A) 20% AgNCls/PMAA; (B) SDF 38% (Fagamin, Tedequim, Córdoba, Argentina); or (C) without treatment. AgNCls/PMAA or SDF were applied on the exposed surfaces with a microbrush for 10 s. Samples were incubated for 24 h at 37 °C at 100% relative humidity. Surface color was measured according to the CIE-L*a*b* system before and after demineralization (R0 and R1), 24 h and one week after treatment (R2 and R3), using a spectrophotometer (CM-600D Konica Minolta Sesing Inc., Japan). Groups A and B received an extra application of AgNCls/PMAA or SDF before a conventional GIC (Fuji IX-Gold Label, GC Corp, Tokyo, Japan) was bonded using a mold, 4 mm diameter × 3 mm high. For SBS, a Universal Testing Machine (Digimess RS-8000-5, China)—crosshead speed of 1 mm/min—was used. Statistical analysis was performed using ANOVA, Student-t and Scheffe-test at a significance of p < 0.05. Group A presented a stable color p = 0.24 between R1-R2 and R1-R3 in contrast to significant color changes in Group B (p = 0.02). SBS was higher (p < 0.01) in Group A (10.4 ± 2.7 MPa) compared to Groups B (3.3 ± 1.3 MPa) and C (4.0 ± 0.4 MPa), where no differences between the latter groups were observed (p = 0.77). Results of this preliminary study demonstrated that 20% AgNCls/PMAA did not stain simulated carious dentin and improved SBS of the GIC. The relevance of this study relies on the development of a therapeutic system to potentially arrest caries lesions without staining.